Lyme disease in cats is rare, though cases have been reported. In a limited study, one third of feline blood samples were found to test positive for Lyme disease. It is probable that some cats are able to resist the illness.

Of reported cases, symptoms exhibited were: pain and stiffness in limbs and joints, lameness, fever, loss of appetite, fatigue, possible sudden collapse, a "zombie-like" trance and in cases of heavy infestation, severe anemia. Most cases are diagnosed because the owner has actually found a tick; otherwise symptoms tend to be ambiguous or other illnesses are suspected.

I know in dogs and cats it is treated with an antibiotic Doxycycline (sp?), not sure about cats.